An exhaust gas sensor may be positioned in an exhaust system of a vehicle to detect an air-fuel ratio of exhaust gases exiting an internal combustion engine of the vehicle. Exhaust gas sensor readings may be used to control operation of the internal combustion engine to propel the vehicle. Specifically, fuel injection amounts to the cylinders can be adjusted in response to the detected air-fuel ratio. Degradation of an exhaust gas sensor may result in increased emissions and/or reduced vehicle drivability. Accordingly, accurate determination of sensor degradation particularly prior to delivering the vehicle for road operation may provide enhanced engine operation.
The inventors herein have recognized the above issues and identified approaches to at least partly address the issues. In one example, a method comprises categorizing each respective concentration of a plurality of exhaust gas constituents measured by a gas analyzer into one of oxidants or reductants, the gas analyzer receiving exhaust gas flow from an engine. The method also includes determining an exhaust air-fuel ratio based on the categorized concentrations and validating output from an exhaust gas sensor receiving exhaust gas flow from the engine based on the determined exhaust air-fuel ratio.
For example, an engine controller in a vehicle on a test bench and a gas analyzer may each communicate separately with a validation controller. The gas analyzer may measure the concentration of individual constituents of tailpipe emissions exiting the vehicle and transmit the individual constituent concentration data to the validation controller. These individual concentrations may be categorized into one of oxidants or reductants and a first air-fuel ratio may be determined by the validation controller based on the categorized constituents. This first air-fuel ratio may then be compared to an output (e.g., an air-fuel ratio) of an exhaust gas sensor exposed to exhaust gases within the vehicle exhaust system. The comparison may be made such that the first air-fuel ratio and the exhaust gas sensor output are time synchronized and therefore refer to the same portion of exhaust gas. Exhaust gas sensor degradation may be confirmed if a difference is detected between the two air-fuel ratios.
In this way, a degraded exhaust gas sensor may be detected prior to putting the vehicle into operation on the road. By determining individual concentrations of a plurality of exhaust constituents with a gas analyzer, a more accurate air-fuel ratio can be calculated, allowing a more robust determination of exhaust gas sensor degradation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.